Ukraine 's President returned to work Monday after four days of sick leave as neighbor Russia called on protesters who have tried to curb his powers to stop their `` threats and ultimatums . ''

President Viktor Yanukovych , who went on sick leave last Thursday for `` acute respiratory disease , '' is seeking a way out of a deepening political crisis that has paralyzed Kiev , the capital .

Thousands of anti-government demonstrators have packed Kiev 's Independence Square since November , underscoring tensions in a country split between pro-European regions in the west and a more Russia-oriented east .

Last week , in the first concessions made by the government , the Prime Minister and Cabinet resigned , a controversial anti-protest law was repealed , and Yanukovych signed off on a contested amnesty bill for anti-government protesters .

But opposition leaders , who have received backing from the U.S. and EU governments , are pressing for more concessions .

In a statement Monday , Russia 's Foreign Ministry told protesters who have set up tents and barricades in the central Independence Square to halt their `` provocative steps . ''

It said one protest leader 's calls for street patrols and the blocking of public buildings `` contradicted statements about the opposition 's commitment to the democratic and European values . ''

`` We hope the opposition in Ukraine will renounce threats and ultimatums and activate a dialogue with the government to solve the severe crisis , '' the ministry said .

Special session in Parliament

Yanukovych 's online press service said Sunday that he was now feeling `` good '' after treatment and his condition had been assessed as `` satisfactory . '' It said he would return to his desk Monday .

The government 's attempts to crack down on the protests appear only to have strengthened the opposition 's resolve . Violent confrontations flared after a sweeping anti-protest law was signed two weeks ago , followed by an uneasy standoff on the streets as the battle in the political arena has heated up .

Yanukovych has resisted calls for him to step down and defended the government 's handling of the political crisis .

However , opposition parties continue to call for constitutional reforms to shift power away from the President and say a new amnesty bill -- which comes into force only if protesters vacate seized government buildings and unblock roads and squares -- is unacceptable .

A special parliamentary session is scheduled for Tuesday .

Activist treated in Lithuania

Deadly clashes last month were an escalation of weeks of largely peaceful public protests prompted by Yanukovych 's decision in November to spurn a planned trade deal with the European Union and favor Russia instead .

He and Russian President Vladimir Putin agreed on a $ 15 billion deal for Russia to buy Ukrainian debt and slash the price of natural gas .

The violence on the streets has raised alarm among Ukraine 's neighbors and Western governments , who have been calling for a peaceful resolution to the unrest .

Western leaders last week also voiced growing concern about reports of the kidnapping and torture of opposition activists in the country .

One , the visibly battered Dmytro Bulatov , reappeared Thursday , more than a week after he went missing . He told reporters he 'd been kidnapped and tortured by his captors -- who , he said , `` crucified me '' by piercing his hands -- before they dumped him in a forest .

EU foreign policy chief Catherine Ashton and White House press secretary Jay Carney condemned his cruel treatment . Ukraine 's Interior Ministry has said it is investigating what happened to him .

Bulatov on Sunday flew to Lithuania for medical treatment , protest leaders said .

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Ukrainian President returns to his desk after a four-day sick leave

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Russia : `` We hope the opposition in Ukraine will renounce threats and ultimatums ''

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Thousands of demonstrators remain on the streets of central Kiev

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The opposition wants more concessions from the government